For BA, JFK is an interesting outstation because it basically has to perform a fairly singular function - force 9-10 departures to a single city through departure formalities every evening from about 6-11pm at an approximately ~30 minute frequency. There's no range of destinations through the day, there's no airside transfer (so people shouldn't be spending extended periods in the departure lounge) and so on. People turn up to the terminal and can pretty much leave on the next flight (in fact that's why JFK is normally excellent at IRROPs, the staff basically have a finite number of ways to get their passengers out that evening and therefore will demonstrate good flexibility in their efforts to go about achieving it...I have turned up at 6pm for a 10pm departure when it's been snowing and the staff put me on the 7pm just to get me out of the way so my seat could be used by someone else later in the evening).
As a result I don't really understand the opprobrium generated by it, it serves a function pretty well - apart from the 20-25 minute queues at around 5pm on a Thursday evening which they could do to improve, I think they can leave well alone. I like being able to turn up at an hour to go, quickly through security and then a short walk to the lounge for a drink and then a short walk to the plane. For regular travellers this is a feature, not a bug. If BA moved into the hangar like T8 I think it would be a retrograde step.